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Water quality

Good water quality is vital to ensure the Murray–Darling Basin’s water is suitable for drinking, agriculture, recreation and the environment.

Water management and land-use practices, as well as natural processes, affect water quality in this large and complex river system.

Key facts

More than 3 million Australians rely on Murray–Darling rivers and their tributaries for drinking water.

Good-quality water powers $24 billion of primary production across the Basin every year.

Clean, fresh water sustains more than 120 waterbird species and 46 native fish species, many unique to Australia.
Across the Basin, 30,000 wetlands, including internationally significant ones, rely on quality water for their continued existence.

Poor water quality can adversely affect water-based recreational tourism, and the communities that depend on good water quality.

Water quality in the Basin is improving due to better management techniques.


Water quality is generally good throughout the Basin but can be compromised by a number of threats, including high salinity, blue-green algal blooms, low dissolved oxygen levels, nutrients and turbidity.

Natural events such as droughts, floods and high temperatures can also quickly degrade water quality.

Measuring water quality

The presence of contaminants and the characteristics of water are used to indicate the quality of water. These water quality indicators can be categorised as:

  • Biological – bacteria, algae
  • Physical – temperature, turbidity and clarity, colour, salinity, suspended solids, dissolved solids
  • Chemical – pH, dissolved oxygen, biological oxygen demand, nutrients (including nitrogen and phosphorus), organic and inorganic compounds (including toxicants)
  • Aesthetic – odours, taints, colour, floating matter
  • Radioactive – alpha, beta and gamma radiation emitters.

Measurements of these indicators can be used to determine, and monitor changes in, water quality. These measurements can also determine whether water quality is suitable for the health of the natural environment and it’s specific uses.

The design of water quality monitoring programs is a complex and specialised field. The range of indicators that can be measured is wide and other indicators may be adopted in the future.

Threats to water quality

Potential threats to water quality in the Basin include:

  • Salinity – salinity occurs naturally when salt levels are increased by irrigation and land clearing, this can affect the health of the environment, reduce drinking water quality, and affect crops and livestock.
  • Blue-green algae – this is found naturally in fresh water but can be made worse by factors, such as elevated water temperatures, sunny days and nutrient loads. These conditions can lead to algal blooms, which pose a serious risk to both human and animal health.
  • Low oxygen – in floods, nutrient rich ‘litter’, such as leaves and branches, is washed into rivers. In some circumstances, breakdown of this organic matter can quickly consume the oxygen in the water, creating a phenomenon called ‘hypoxic blackwater’ which can kill aquatic life (such as fish, turtles and crabs) in large numbers.
  • Nutrients – elements such as phosphorus and nitrogen enter the Basin’s waterways through agricultural activity, stormwater runoff or erosion, and can stimulate algal growth.
  • Turbidity – when matter suspended in water, including sediment introduced by erosion or stirred up by carp, reduces light penetration, affecting plants and animals in the water.
  • Temperature – cold water released from dams in summer can damage ecosystems. Conversely, warmer temperatures in summer can also be harmful and encourage blue-green algae growth.

Managing water quality

Good water quality is crucial for a healthy environment, productive industries and for providing suitable drinking water.

Managing flows, wherever possible, can help to mitigate salinity, turbidity, fluctuating water temperature and dissolved oxygen shortages.

Some of our most ecologically valuable waterways cross state and territory borders. Good water quality management requires us to work together across all levels of government, and with our industries and communities.

Water quality is managed in partnership by the Australian Government and the Basin state and territory governments.

At the local level, communities and landholders are working together, with the Murray–Darling Basin Authority and local and state governments, to reduce salinity and improve water quality overall.

Water resource plans are required to include water quality management plans. These plans identify key causes of water quality degradation and risks to water quality and incorporate water quality and salinity targets. They also specify cost-effective measures that will be undertaken to achieve water quality objectives.

Water quality targets are set out in the Murray–Darling Basin Plan, the Murray–Darling Basin Agreement and the Water Quality Guidelines, under the National Water Quality Management Strategy.

Salinity can be managed by improving farming systems and operating salt-interception schemes. Currently, 18 schemes divert about half a million tonnes of salt away from the rivers and adjacent landscapes every year.

Every year the Murray–Darling Basin Authority assesses performance against water quality targets and looks for trends over time.

Basin governments apply an adaptive management approach to water quality, using new information, trialling techniques and making changes as needed.